Masking stripes in Vegas

Hello!

I'm currently working on a little movie. I have shot a few clips in the same camera angle so I can cut in myself in one clip. It's a tricking movie, and I'm doing it in front of a cloudy sky. The problem is now, as you might suspect, that the clouds are moved differently in all of the clips. I come up with a solution, I changed the "Bump Map" so that the sky turned all white and shiny, so that the clouds become a white sky. I think that this is a little too bright and shiny on rhe grass and myself, so I found this good plug-in "Levels" so I can make everything else more darker and sharper, but the sky still is shiny. The thing is, as I'm masking, that there is stripes now from the masking, which weren't before (the camera angle doesn't change, as said), and they wont go away however I do.

So this is my problem: I want the clouds turned into one white shiny sky, and the ground and me sharp and darker, and I want the stripes from the masking gone.